RAPID PROTOTYPING & MANUFACTURING

March 13, 2011

We are always trying to find new methods to do “old” things. This fact is true for most professions and certainly for the engineering and manufacturing disciplines. The term “best practice” was coined by manufacturing engineers to describe the art of doing it better. Better usually means faster, with fewer people and certainly with less expense. Meeting and/or coming under your speficied budget will give an engineer, and certainly an engineering manager, “hero status”. No two ways about it. When I worked for the General Electric Company, we had a “million dollar club”. The engineer who saved the company a million dollars got to keep his job. ( Just kidding here but I’m not too far from being correct! )

There is one technology available today that can “kick the can down the road” and provide those coveted dollar savings we all get famout for–RAPID PROTOTYPING.

Rapid prototyping is definitely a technology that has, and is, changing the way companies and commercial entities do business. We can certainly say this “emerging technology” has gained tremendous momentum over the past decade. The applications and uses represent a “best practice” for manufacturers and producers in general.

Being able to obtain prototype parts quickly allows a company to test for component form, fit and function and can help launch a product much faster than your competition. This can allows for adjustments in design, materials, size, shape, assembly, color and manufacturability of individual components and subassemblies. Rapid prototyping is one methodology that allows this to happen. It also is an extremely valuable tool for sales and marketing evaluation at the earliest stages of any program. Generally, an engineering scope study is initially performed in which all elements of the development program are evaluated. Having the ability to obtain parts “up front” provides a valuable advantage and definitely complements the decision making process. Several rapid prototyping processes are available for today’s product design teams while other prototyping processes utilize traditional manufacturing methods, such as 1.) CNC Machining, 2.) Laser Cutting, 3.) Water Jet Cutting, 4.) EDN Machining, etc. Rapid prototyping technologies emerged in the ‘80s and have improved considerably over a relatively short period of time. There are several viable options available today that take advantage of rapid prototyping technologies. All of the methods shown below are considered to be examples of rapid prototyping and manufacturing technologies.

(SLA) Stereolithography

(SLS) Selective Laser Sintering

(FDM) Fused Deposition Modeling

(3DP) Three Dimensional Printing

(Pjet) Poly-Jet

Laminated Object Manufacturing

All six (6) of the technologies given above require the following preparatory steps:

Create a 3-D model of the component using a computer aided design (CAD) program. There are various CAD modeling programs available today but the “additative manufacturing” process MUST begin by developing a three-dimensional representation of the part to be produced. It isimportant to note that an experienced CAD engineer/designer is an indispensible componentfor success. As you can see, RP&M processes were required to wait on three-dimensional modeling before the technology came to fruition.

Generally, the CAD file must go through a CAD to RP&M translator. This step assures that the CAD data is input to the modeling machine in the “tessellated” STL format. This format has become the standard for RP&M processes. With this operation, the boundary surfaces of the object are represented as numerous tiny triangles. (VERY INDENSIBLE TO THE PROCESS!)

The next step involves generating supports in a separate CAD file. CAD designers/engineers may accomplish this task directly, or with special software. One such software is “Bridgeworks”. Supports are needed and used for the following three reasons:

To ensure that the recoater blade will not strike the platform upon which the part is being built.

To ensure that any small distortions of the platform will not lead to problems during part building.

To provide a simple means of removing the part from the platform upon it completion.

Next step— the appropriate software will “chop” the CAD model into thin layers—typically 5 to 10 layers per millimeter (MM). Software has improved greatly over the past years and these improvements allow for much better surface finishes and much better detail in part description. The part and supports must be sliced or mathematically sectioned by the computer into a series of parallel and horizontal planes like the floors of a very tall building. Also during this process, the layer thickness, as discussed above, the intended building style, the cure depth, the desired hatch spacing, the line width compensation values and the shrinkage compensation factor(s) are selected and assigned.

Merging is the next step where the supports, the part and any additional supports and parts have their computer representations merged. This is a crucial and allows for the production of multiple parts connected by a “web” which can be broken after the parts are molded.

Next, certain operational parameters are selected, such as the number or recoater blade sweeps per layer, the sweep period, and the desired “Z”-wait amount of time is selected. “Z”-wait is the amount of time in seconds the system is instructed to pause after recoating. The purpose of this intentional pause is to allow any resin surface nonuniformities to undergo fluid dynamic relaxation. The output of this step is the selection of the relevant parameters.

The last step is to “build the model”

As you can see, this is a specialized technology and one dependent upon state of the art computer aided drawings, laser technology and a fairly new engineering called mecatronics–the combination of mechanical enginnering and electronics. In short–WE NEED INDIVIDUALS WHO CAN BE TRAINED ! to maintain our competative edge.

Hello Rpprototype-I really appreciate you taking a look. You would not believe the number of favorable comments I have received from this post. Apparently readers really enjoy the topic. I follow Rapid Prototyping on a day to day basis and can tell you the technology is quickly improving–certainly the materials used for the models. Again, many thanks and take care.